Modifying acetyl-celluloses.



.niZtIL KNOEVENAGEL, or HEIDELBERG; GERMANY, ASSIGNOR TO THE FIRM or KNOLL AND COMPANY, OF LUDWIGSHAFEN-ON-THE-RHINE, GERMANY.

MODIFYING ACETYL-GELLULOSES.

No Drawing.

heating and in a dissolved or at least' strongly swelled state acetyl celluloses which hydrids,

obtained.

I seminated that in the case of acetyl cellu-' are-insoluble in acetone. This conversion may be carried out with advantage in the presence of disintegrating catalysts possessing a weak hydrolyzing action, such as sulfates, bisulfates, chlorids or nitrates with or (in the absence of acid anhydrids) without the presence of water or even by water alone without a catalyst. In the presence of acid anhydrids the water may-be replaced by other substances which decompose acid ansuch as alcohol, glycerin, etc. The process is based upon the new knowledge that the saponification and still more the hydrolytic decomposition of acetyl cellulose must take place at the very most to. a slight degree only in the transformation of acetyl celluloses insoluble in acetone into products soluble in acetone, if valuable acetyl-celluloses viscidly soluble in acetone are to be Hitherto the opinionhas been widely disloses insoluble in acetone it was necessary, that partial saponification or hydrolysis or both should take place, in order to obtain from them acetyl celluloses soluble in acetone. All the earlier processes which have become known follow this view. In all the older processes therefore a strong sapon'ifying or hydrolyzing action or both was always exerted. Thus for example according to the specification of French Patent No. 371447 insoluble acetyl celluloses are heated with aqueous strong acids, until they have become soluble in acetone. In the specification of American Patent No. 838350 also water is used in the presence of sulfuric acid (which exerts a very strong saponifying and hydrolyzing disintegrating action) and simi- Specification of Letters Patent.

Patented Oct. 2, 191?.

Application filed January 29, 1913. I Serial No. 745,005.

lar substances for the transformation of acetyl-celluloses insoluble in acetone into. the soluble forms. In all these processes the water exerts a highly injurious collateral action owing to the strongly hydrolytic effect of the sulfuric acid and similar agents.

Just as the acetolytic action of the sulfuric acid has to be tempered by half or wholly neutralizing itwith bases in the acetylation of cellulose, so must also the hydrolysis be modifiedin the conversion of acetyl-celluloses which are insoluble in acetone into those forms which are soluble in acetone.

In the specification of French Patent No. 14558 (patentof addition to French Patent No. 432046) the conversion of acetyl-celluloses which are insoluble in acetone into soluble products is effected merely by acid salts of sulfuric acid. In the said patent however'and in contradistinction to the present process, they are used in the presence of a large quantity of water. If the directions given in the'said patent for nitric acid for example be followed, using sodium bisulfate instead of nitric acid, (and even using primary solutions of acetyl cellulose in the same process) the valuable acetyl celluloses which can be prepared. according to the present process are not obtained. It was necessary first to know, that hydrolysis of the acetyl cellulose molecule is not only a subordinate factor in the formation of products soluble in acetone, but is even injurious to the valuable viscidly soluble and elastic acetyl celluloses. When sulfates with a weak hydrolytic action are used, the quantity of water may, as follows from the same knowledge,

and short of producing an injurious hydrolytic disintegration, be considerably increased in comparison with the quantities of water used with bisulfates, although the quantity of water even in this is by far not so great as that employed in the process de scribed in the specification of French Patent No. 14558 and may even be omitted alto- %ether in the absence of acid anhydrids.

' tions still containing acetic acid anhydrid the primary solutions, other substances which into special channels, owing to the absence of large quantities of water and strong saponifying'agents, which channels are less characterized by saponification andhydrolytic disintegration of the cellulose molecule, than by otherreactions, probably intramolecular rearrangements.

The present process may therefore be carried out in a great variety of ways. The only condition is, that the additions of the catalyst with or without water, and even without the catalyst, be so proportioned that all saponifying or acetolytic action on the acetyl cellulose be retarded as much as possible. I L

If in the present process primary solube started from, it will be necessary to take care in each case that the acid anhydrid is. destroyed firstas soon as possible,'as other-,

wise the acid anhydrid will produce collateral acetolysis of the cellulose molecule, whichalways leads to the formation of a cetyl celluloses which are of considerably less value and less viscidly soluble in acetone. The ..removal of the anhydrid may be effected both by the addition of water to as well as by any easily undergo decomposition with acid anhydrids. When water is used to destroy the acid anhydrid, it is always necessary to use a certain excess .over and above the theoretically necessary quantity. In the presence of catalysts witha saponifying or hydrolytic action this excess must not, however, be as great as that stated in-the specification of French Patent No. 14558. In the presence of other salt composed directly for the conversion of substances instead of water, such as alcohol, I 40 glycerin, the acetins, etc., no such limitation is necessary on account of the lack of any hydrolytic action.

If the primary solutions contain a mildly acting catalyst this latter may, .if it be already a sulfate, clorid or nitrate, be used the product which is insoluble in acetone into the one which is soluble in acetone. All that is necessary is, to destroy the anhydrid and heat the primary solution further.

If the catalyst employed in the acetylation of the cellulose was sulfuric acid, it must' be decomposed after the acetylation has been effected, either by the addition of a corresponding quantity of a base or ofa of a weak acid and a strong base, such as sodium acetate, so that the sulphuric acid be thereby converted into neutral sodium sulfate and the catalyst moved by the addition of water or the like and further heating of the primary solution is proceeded with, until repeatedly taken samples show a satisfactory solubility in acetone. 7

When adding the water to the primary solution, it is advantageous to do so in such a manner, that it shall be introduced quite gradually and if necessary even in a suitably diluted form, so as to prevent any injurious rise of temperature in the solu- 131011.

If a ready prepared acetyl-cellulose insoluble in acetone be started with, it is preferably dissolved in one of its solvents, such for example as glacial acetic acid, .and to 7 this solution, which may'also if necessary be only a thick magma, may be added a smallquantity of water, alcohol or the like,

or a mildly acting catalyst or both together and the mixture heated at a suitably high temperature, until a repeatedly taken sample has become soluble in acetone.

The process may be explained by the following special examples which, however, as the above description shows, may be modified in many different ways:

1. A primary acetyl-cellulose solution in glacial acetic acid prepared according to the specification of German Patent No. 203178 with methylamin sulfate for example, is mixed with 0.8 parts of water for example to one part of cellulose and then heated to 70 for example, until the acetone-soluble products areformed.

2. As example 1, but insteadof water 1.5 to 2 parts of alcohol, glycerin or the like are added and the solution heated to 70,

/ composition of the excess of acetic acid anhydrid.

3. One part of cellulose is heated according to the Specification of German Patent N 0. 203178 to 100, until solution takes placeywith four parts of glacial acetic acid, 0.1 parts of chlorid of zinc and five parts of acetic acid anhydrid. One part of water is until. a repeatedly taken sample shows that the acetyl-cellulose hasbecome soluble in acetone. Instead of the chlorid of zinc,

other chlorids or nitrates may be used at 70] OI' at other for instancelhigher temperatures. Instead of water, 1 to 2 parts of alcohol or monacetin or other similarly acting sub 130 The temperature for' the converthen added and the mixture heated to 70,-

staiices may be used, so that the anhydrid is completely decomposed.

L. Ready prepared acetyl-cellulose insolu- 1 ble in acetone is heated with glacial acetic acid, or glacial acetic acid containing about 6 to 10% of water, or glacial acetic acid containing from'lO to 20 per cent. of alcohol or the like in the proportion of one :nine to about 100, until a repeatedly taken out sample proves'to be soluble in acetone.

5. One part" of cellulose is acetylated at ordinary temperature up to 70' with five parts of acetic acid anhydrid, six parts of glacial acetic acid and 0.4 parts of methylamin sulfate or nethylamin bi'sulfate or q orthotoluidin-bisultate' containing one molecule of water ofcrystallization, or the like. After the cellulose has dissolved, the acetylcellulose is converted at approximately to 30 with the gradual addition of water into an acetone solubleproduct. I The experiment was carriedlout with 96% glacial acetic acid.

What I claim'is:- 1. The process for-jthe conversion of acetone-insoluble acetyl-celluloses into acetylcelluloses, easily soluble in acetone,'which.

heating the acetone-insoluble in the presence of a substance which will produce only a slight hydrolytic decomposition of the acetyl cellulose until the specified solubility has been producedQsubStantiaIly as described.

2. The process for the conversion of consists in acetyl-celluloses,

. composition witnesses.

acetyl-celluloses insoluble in acetone into acetyl-celluloses easily soluble in acetone,

which conslsts in dissolving the acetone-insoluble acetyl-celluloses in one of their solvents," and heating the solutions, until the specified solubility has been produced,,substantially as described. Z

3. The process for the conversion of acetone-insoluble acetyl-celluloses into acetylcelluloses soluble in acetone, which consists in heating the acetyl-cellulosesinsoluble)- in acetone in the presence of a substance which will produce only a slight hydrolytic decoma position: of the acetyl cellulose and small uantities of water, until the specified solubility has been produced, substantially as described.

4. The process for the conversion of acetone-insoluble acetyl-celluloses into acetylcelluloses easily soluble DB. EMIL ,KNOEVENAGEL. Witnesses:

CARL Wrrrn, I JOSEPH PFEYIZFFEB. I

of Water necessary for the de- 

